It is known that in a process for producing phenyl benzoate or its hydrolytic product, phenol, by the oxidative decarboxylation of benzenemonocarboxylic acid, or its salt, ester, or acid anhydride, a copper compound is used as a catalyst. It is also known that addition of a magnesium compound to the copper compound permits selective production of phenyl benzoate and its hydrolytic product, phenol. The use of such catalyst systems, however, results in the formation of large amounts of high boiling by-products, giving rise to serious problems in that the rate of formation of phenol is reduced with a lapse of time and the recovery of catalyst is reduced. Therefore, in order to increase the selectivity of phenol, various improvements in catalyst have been made. U.S. Pat. No. 3,379,774 discloses that the use of a three component catalyst of copper, magnesium, and manganese increases the rate of formation of phenol and reduces the amount of high boiling point product (pitch) being formed. U.S. Pat. No. 3,637,807 discloses that a copper/manganese catalyst produces large amounts of phenoxybenzoic acid and diphenyl ether, and controls the formation of pitch. British Pat. No. 1,015,077 (corresponding to U.S. Pat. No. 3,277,184) describes that a copper/rare earth element cation catalyst increases the rate of formation of phenol.
A method is also known in which benzenemonocarboxylic acids, or their salts, esters, or acid anhydrides are used as starting materials, and in which the starting material is contacted with molecular oxygen-containing gas in the presence of a catalyst at a first step to form mainly benzenemonocarboxylic acid phenyl esters, and the esters are hydrolyzed at a second step to obtain phenols (see U.S. Pat. No. 3,929,911). This method is called a "two-step reaction method". It is said that the two-step reaction method is an energy-saving process whereby the amount of steam used in the hydrolysis reaction can be markedly saved compared with a one-step reaction method in which the oxidation reaction and the hydrolysis reaction are performed at the same time in the same reactor. However, when the above-described known catalysts are used in the two-step reaction method, large amounts of high boiling point by-products are formed as is the case with the one-step reaction method, resulting in a reduction in yield. This presents problems in that the rate of formation of phenol is lowered with a lapse of time and the recovery of catalyst is reduced.